Electronic object detector



Jan. 26, 1965 J, I R ETAL 3,167,739

ELECTRONIC OBJECT DETECTOR Filed May 19, 1960 2 Sheets-Sheet 1 F l G. 3

u: 2 J o L TIME lACKGROUND OBJECT DETECTION BACKGROUND 4 F e. I 2

/ INVENTORS.

6 LARRY J. GIRARD NORMAN L. STAUFFER ATTORNEY.

J 1965 L. J. GIRARD ETAL ELECTRONIC OBJECT DETECTOR 2 Sheets-Sheet 2 Filed May 19, 1960 I I I I I I l I I l l I l I I I l I I I I l I United States Patent 3,167,739 ELEiITRGNiC OBJECT DETECTOR Larry J. Girard, Littleten, and Norman L. Stautier, Denver, (1010., assignors to Honeywell Inc, a corporation of Delaware Filed May 19, 196i}, Ser. No. 30,125 7 Claims. (6i. 349-68) This invention relates to electronic apparatus, and more particularly to electronic counting and control apparatus.

In the complex relationships of modern activities, it becomes increasingly important to provide automatic means for taking count of and controlling the movement of individual items. An example of a situation requiring such improved counting and control means is the flow of vehicular traflic on our streets and highways. A wide range of conditions are imposed upon systems designed for this purpose. First, the system must be reliable under various conditions of ambient lighting, from brilliant sunlight to dark of night; under various conditions of arnbient temperature, from tropic heat of summer to the freezing cold of winter. It must be capable of producing a reliable signal under various conditions of road surface including blacktop, macadam, or concrete. The situation is further complicated in that the signals must continue to be reliable even though the ambient conditions change considerably. For example, one condition is presented to the system when the roadway is hot and dry, a considerably different ambient condition prevails during and followinga rain or snowfall, leaving the roadway either wet or snow covered. Again, the situation is still further complicated by the variations in velocity and frequency of the passage of the vehicles as well as the variations in the spacing between vehicles. It is an object of the present invention to provide an improved system for sensing and signaling the passage of objects past a sensing station.

It is another object of this invention to provide a sensing and signaling system as set forth which is especially adapted for use as a roadway vehicular traific sensing and signaling system. 7

It is a further object of this invention to provide an improved trailic sensing and signaling system which is capable of meeting all of the requirements set forth above.

Previous traflic sensing and signaling devices have, for one reason or another, required considerable ancillary hardware for their installation such as pressure plates imbedded in the roadbed or special support poles and means, such as special mounting arms, to support the sensing means directly over the trafiic lane to be sensed.

It'is a-still further objectof tln's invention to provide an improved trafiic sensing and signaling means which requires little or no ancillary hardware for its installation but may be mounted conveniently high on available utility poles at the side of the roadway and aimed at the lane or lanes to be sensed.

It is yet another object of this invention to provide a trailic sensing and signaling system which is relatively inexpensive in initial cost and in operation and which requires little or no maintenance or attention.

In accomplishing these and other objects, there has been provided, in accordance with the present invention, an object sensing and signaling system which features a source of infra-red radiation and means for focusing the beam therefrom onto the path tobe followed by the object .to be sensed. An infra-red sensing means is positioned 3,lh?,?3 Patented Jan. 26, 1965 circuit is characterized in that the signals developed therein are applied to control the intensity of the radiation from the infra-red source, thereby to maintain the ambient condition seen by the sensing device substantially constant. With this arrangement, the system becomes self compensating for any of the several anticipated conditions as well as for changes in the internal condition of the apparatus. 1

A better understanding of this invention may be had from the following detailed description when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a graphical representation of a traffic sensing and signaling system embodying the present invention and shown in situ; I

FIG. 2 is a schematic circuit diagram of a system embodying the present invention; and

FIG. 3 is a graph representing certain signal relationships occurring in the circuit shown in FIG. 2.

Referring now to the drawings in more detail, there is shown in FIG. 1 a representation of a traffic sensing and signaling means 2 mounted on a utility pole 4 by the side of a roadway 6. From the apparatus 2 there is shown a broken line 8 representing a beam of infrared radiation, emanating from the apparatus 2, impinging on the surface of the roadway, and, because of the inherent roughness of the road surface, being reflected, at least in part, back to the apparatus 2. As a vehicle passes along the roadway and into the beam 8, the character of the reflected beam will be changed, as will be more fully set forth hereinafter, by the surface of the vehicle. The apparatus 2 detects this change in reflection to produce a signal in accordance therewith. The signal thus produced may be used to actuate a counter which may, in turn, be used to merely accumulate statistical data or may he used to automatically program the actuation of associated traffic control signals.

Suitable apparatus for the sensing and si naling means 2 is shown in substantial detail in FIG. 2. An infra-red radiation sensing means such as a lead-sulphide cell 10 is positioned to receive radiation from the surface of the roadway 6 (FIG. 1) through suitable focusing optics represented by a lens 12. The cell 10 is connected at one end to a power supply bus 14 and, at the other end is connected to ground through the primary winding 16 of a coupling transformer 18. The transformer 13 has a secondary winding 20 to which is coupled the input stage 22 of a transistor amplifier. The transistor amplifier further includes, as successive stages of amplification transistors 24, 26, 28 and 3%. Between the output of the transistor 26 and the input of the transistor 23 there is connected a series tuned coupling network ineluding a capacitor 32 and an inductor 34. As will be shown hereinafter, the control signal applied to the input of the system is chopped at a predetermined frequency, say 400 cycles per second. The just mentioned tuned network is tuned substantially to that frequency to elin1- inate the effect of spurious signals on the subsequent elements of the system.

The output of the last stage 3t? of the transistor amplifier is coupled to the primary winding 36 of a coupling transformer 38. The transformer 38 has a center-tapped secondary winding 40. Each of the extreme ends of the secondary winding 40 of the transformer 38 is connected to the base electrode of a transistor 42., 44 respectively. The center-tap of the secondary 46) is grounded. The emitter electrodes of the two transistors 42 and 44 are connected through a suitable filter to ground; The two collector electrodes are connected together to provide a DC. output signal which is a function of the signal detected by the detector element it). Thus, the

anew/s9 transformer 33 and the two transistors 42 and 44 constitute a full-wave rectifier circuit. 1

The rectified output from the rectifier is applied through a series of crystal diodes to a corresponding group of transistors. A first crystal diode 46 is connected between the output of the rectifier and the base electrode of the transistor 48. Similarly, this second diode 51) is connected between the output of the rectifier and the base electrode of the transistor 52. Again, diode 54 is connected between the output of the rectifier and the base electrode of the transistor 56. And further, diode 58 is connected between the output of the rectifier and the base electrode of the transistor 69. With the foregoing arrangement the output signal from the rectifier may be applied to each of the four transistors with the crystal diodes pro viding the necessary isolation to prevent interaction be tween the respective transistors. transistors 4d and 52 are of one conductivity type while the transistors 56 and 6d are of the opposite conductivity. The purpose of this arrangement will appear more fully hereinafter.

The bias voltage for these four transistors as well as for subsequent transistors is obtained by a voltage divider comprising a series string of resistors connected between the negative voltage supply V and ground. These resistors 62, 64, 66, 68, 7t) and 72, respectively, are arranged to give progressively diflerent levels of bias signal as will be seen to be necessary. Thus the emitter of the transistor 48 is connected to the junction between the resistors 7t) and 72. The emitter of the transistor 52 is connected to the junction between the resistor 68 and 7 t). Similarly, the emitter of the transistor 56 is connected tothe junction between the resistors 64 and '66, while the emitter of transistor 69 is connected to the junction between resistors 62 and 6 The junction between resistors 6d and 68 is nominally at the same static level as the rectified output from the transistors 42 and 44.

The collector output'of the transistor 48 is applied to the base input of a subsequent transistor 74. Similarly I It will be noted that the and the collector output of the transistor 56 is connected to the base input of the transistor fill. The collectorof the transistor '74 is connected to the V supply line while the collector of transistor 76A is connected to ground. The junction between the resistors 66 and 68,

forming the bias voltage-divider center point, is connected through a first crystal diode'82 to one end of the coil 84 of the relay 86. The emitter of transistor 74 is also connected to the'sarne end of the relay coil 84. The same junction between the resistors, 66 and 68, is also conit is to be noted the diodes S2 and 88 are of ly a capacitor 92 is connected between the emitter and the collector of the transistor '76. The junction between the resistors 66 and 68 is also connected to the emitters of both transistors 78 and 34 the two emitters being connected together. The collector of the transistor 7 8'is connected through the energizing coil of a relay 94 to the V-' 7 power supplyline. A capacitor 96 is connected between thecollector and the base of'the transistor 73. In-a like manner, the collector of the transistor S43 is connected through" the energizing coil'of a relay 9% to ground. 'The capacitor 1% interconnects the base and the collector of the transistor-8h. Relay 86 when energized controls the actuation of a movable blade 102'between a pair offixed contacts 1&4. These three contacts are arranged for connection to a suitableutilization apparatus as an output means.

' The relay 94 also includes a movable blade operating 4 between a pair of fixed contacts, as does the relay 9%. The movable contact of the relay 94 is directly connected to the movable contact of the relay 98. The upper or normally closed contact ofthe relay'94 is directly connected to the upper and normallyclosed contact of the relay 9%. Both of these contacts are connected toone terminal of an alternating current source. The lower and normally open contact of the relay 94'is connected through the field winding 198 of a low speed synchronous motor to the other terminal of the alternating currents source. Similarly the lower and normally open contact of the relay 98 is connected through the field winding 112 of a substantially identical motor 114 to the opposite terminal of the alternating current source. The motors 11d and 114 are arranged for rotation in opposite directions with respect to each other when one or the other is energized by the closing of the relay 94 or the relay 28, re-

spectively.

The motors 110 and 114 are arranged to control the position of a slider 116 along a slidewire 118. The slidewire 118is connected in a voltage divider 'across the outputof the power'supply source. The supply source includes means for connection to an A.C. source 120 which is connected to the primary winding of a transformer 122. The secondary winding of the transformer 122 is connected in a conventional full-wave rectifier arrangement with a pair of diodes 124 and suitable filtering. The voltage divider network including the slidewire 118 is connected across the output terminal of this full wave This shutter element is represented as a rotary member which is in turn driven ata constant speed by a suitable motor 134Which is shown connected directly across the A.C. input leads.

Inasmuch as it is anticipated'that the present apparatus will be used" under extremes of climatic conditions including those of extremely low and icy conditions'there has been provided a pair of heater elements 136 and 138' respectively connected across the A.C. supply leads and energized through actuation of a thermostatic switch 140.

These heater elements are arranged to prevent the formation of ice and snow on the optical'system.

In operation .it islassu'medthat the infra-red bulb 128 is emitting a predetermined amount of radiation chopped by the chopper 132and focused by'thelens on the roadway- 6. "A portion of the choppedi'infra-reidfemission impinging onthe'roadway is reflected back through.

the lens 12 onto the" sensing element 10. The element 10 is characterized in that the resistance thereof tocurrent flow is changed in accordance with, the arnountof radiation inwimpinging thereon. It will be remembered This 400 cycles 'per' second signal is coupled through the tr-ansformer18 to the input stage 22 of the transistor arnplifier.-1The. effect of 'all random". radiation other than the 400 ,cycle per' second signal is eliminated through the tuned circuit including the capacitor 32 and the'inductor 34. Thus the signal'fed to the primary. 36

- of thet'ransformer 38 isrepresentative of the background illustrated in FIG. 3 asthatp'ortion of'the signal rep-1 resented asfbackground. It will be noted thatthis signal as received fromthe roadway6. This signal is Interposed in the. beam of radiation emitted by the bulb'128 is a suitable light chopper represented by the shutterelement 132.

signal falls between the dotted lines b and c in so far as the amplitude indication is concerned. Considering only this portion of the signal as it effects the remainder of the apparatus, it may be seen that this signal is fed to the rectifier including the transistors 42 and 44. 'Let it be assumed that the V supply has a value of 20 volts. The static output condition of the rectifier is chosen to be at 10 volts. The bias values established for the transistors 52 and 56 by the voltage divider resistors 62 through 72 are such that these two transistors are biased into heavy or saturated conduction. With this conductivity condition of the transistors 52 and 56, the transistors 78 and 80 are biased to cut-oflf and both relays 94 and 98 remain unenergized. Assume now that the amplitude of the signal fed to the primary 36 of the transformer 38, for some reason or another, increases slightly over a long term period. This increase in signal will be expressed as an increase in the signal level put out by the rectifier and applied as input to the transistor 52. The increasing signal applied to the base of the transistor 52 reduces its conductivity, thereby changing the bias on the transistor 78, allowing it to become conductive, the emitter of the transistor 78, being referenced to the center point of the voltage divider represented by the resistors 62 through 72. As the transistor 78 becomes conductive, current flowing therethrough flows also through the energizing coil of the relay 94. This causes the relay 94 to be picked up, thereby energizing the winding 108 of the motor 110. Energizing the motor 110 causes the slider 116 to move along the slidewire 118, and change the bias on the transistor 126. This change in bias on the transistor 126 reduces the current flowing therethrough and accordingly reduces the current flowing through the infra-red radiation source 128. This reduction in the amount of radiation from the source 128 will be of an amount necessary to oifset whatever caused the increase in signal applied to the input of the transformer 38. When the output of the rectifier has again reached a nominal value substantially equal to the center point of the voltage divider, i.e., approximately l volts in our illustrative, example, transistor 52 will resume its heavy conduction, again biasing the transistor 78 to cutoff.

' Similarly if the signal applied to the input of the trans- 1 former 38 had decreased the transistor 56 would have been operated at a reduced conductivity condition and would thereby have biased transistor 80 into a state of conduction, thereby causing the relay 98 to be picked up. This would, in turn, have energized the winding 112 of the motor 114 causing the slider 116 to move in the opposite direction along the slidewire 118, thereby causing the conductivity of the transistor 126 to increase and, in turn, increasingr-adiation emitted by the memher 128. It may be seen through the foregoing operation, the apparatus herein described is automatically rotation of approximately 4 revolutions per hour, thus, providing an integrated output of the ambient condition of the system which has an efiective integration time constant of relatively long duration.

Now let it be assumed that the system has stabilized itself, as aforesaid, and that a motor vehicle passes along the roadway interrupting the reflection pattern of vthe infra-red beam. Because of the complexity of the contours of the shiny surfaces of modern automobiles, the

reflection to the sensing element may be either increased appreciably or decreased appreciably, depending on whether the portion of the contour of the vehicle presents a surface which is approximately perpendicular to the infra-red beam or one which is at a substantially smaller angle with respect to the infra-red beam. In fact a single vehicle may present a series of rapidly changing increases and decreases in the reflected signal. These signals as received by the sensing element 18, amplified by the transistor amplifier, and applied to the input transformer 38 are represented in FIG. 3 as the portion of the curve designated object detection. These signals also are applied to the full-wave rectifier where they are rectified and presented to the following circuitry much in the manner of the signal previously described. Since these signals are of substantially higher frequency characteristic than the one previously described the capacitors 96 and prevent them from appreciably influencing the operation of the motors and 114. However, they are applied to the input of the transistors 48 and 60. Much in the manner of the operating characteristic of the transistors 52 and 56, transistor 48 and 60 are also biased into heavy conduction. There is one significant difference between the operation of transistors 48 and 60 as distinguished from that transistors 52 and 56. That is that the bias to be overcome by the input signal is considerably higher in the case of the transistors 48 and 60 than in the case of the other two. This bias level is represented by the dashed lines d and e in FIG. 3. Thus if the signal increases beyond dashed line d of FIG. 3 the conductivity of the transistor 48 will be reduced thereby, biasing transistor 74 into conduction. When the transistor 74 conducts, its current path may be found to flow from the center point of the voltage divider resistor string, that is, the junction between resistors 66 and 68 through the diode 88, the exciting winding 84 of the relay 86, thence to the emitter and collector of the transistor 74. Thus, when the transistor 74 is rendered conductive, the relay 86 is energized, causing the blade 102 to be transferred from the normally closed position to contact with the other one of the two fixed contacts 104. On the other hand, when the beam is reflected away from the sensing element 10 and the signal applied to the transformer 38 drops below the level indicated by the dash line e of FIG. 3, then the transistor 60 has its conductivityreduced, biasing the transistor 76 into conductivity. The transistor 76 being of the opposite conductivity type from that of transistor 74, we find that its conduction path flows from the collector to the emitter thereof, thence through the energizing winding 84 of the relay 86, through the crystal diode 82, thence to the junction between the resistors 66 and 68. This current flow also causes the relay 86 to be picked up, or, in this case, to remain picked up. The capacitors 90 and 92 connected between the emitter and collector respectively of these two transistors provide a small integrating action to prevent an inadvertent dropout of the relay 86 during the transition of the transfer of conductivity from one of these transistors to the other. When the signal applied to the transformer 38 has again returned, for a significant period, to the amplitude represented as background in FIG. 3, then relay 86 will be allowed to drop out. Thus the complex reflection pattern from a single vehicle causes only a single actuation of the relay 86. Thisin turn produces a single count in the utilization apparatus 106. As liereinbefore mentioned the utilization apparatus 106 may comprise merely a counter for compiling statistical data or the output 1. An electronic sensing and signaling apparatus comprising means for producing a beam of signal radiation, means for directing said beam of radiation toward a path along which an object to be sensed passes, signal produc-v ing means for detecting reflections of said radiations from said path and from said object to be sensed, signal selecting means for distinguishing between signals produced as a result of reflections from said path and signals produced as a result of reflections from said object to be sensed, means responsive to said signals produced as a result of reflections from said path to change the intensity of the radiation from said beam producing means in accordance with changes in intensity of said reflections from said path, and means responsive to said signals produced as a result of reflections from said object to produce an output signal.

2. An electronic sensing and signaling apparatus comprising means for producing a beam of infra-red signal radiation, means for directing said beam of radiation toward a path along which an object to be sensed passes, infra-red radiation sensitive signal producing means for detecting reflections of said infra-red radiations from said path and from said object to be sensed; signal'selecting means for distinguishing between signals produced as a result of reflections from said path and signals produced as a result of reflection from said object tobe sensed, means responsive to said signals produced as a result of reflections from said path to change the intensity of the radiation from said beam producing means in acand from passing motor vehicles, means for amplifying 'signals'produced by said signal producing means, signal selecting means connected to said amplifying means for distinguishing between signals produced ,as a result of reflections from said roadway andsignals produced as a result of reflections from said passing vehicles, means responsive to said signals produced as a result of reflections from said roadway to change the intensity ofradiation from said source in accordance with changes in intensity of the reflections received from said roadway, and means responsive to said signals produced as a result of reflections from said passing vehicles to produce an output signall 4. The invention as set forth in claim 3 wherein said means responsive to signals produced as arresult of reflections from said roadway includes a transistor current control means, a pair of electromagnetic relays, said relays being operable in accordance with the. current control action of said. transistor current control means,

reversible motor means responsive to the actuation of said relays, and means responsive to the operation of said motor means to control the amount of energizing current applied to said source of infra r'ed radiation.

5. The invention as set forth in claim 4'wherein said last mentioned means comprises a slidewire potentiometer "of reflection from said passingvehicles includes a further transistor current control means, a relay, said'relay being operable in accordance with the current control action of said further transistor current control means,

said actuation of said relay'comprising an output signal for said apparatus. 7

7. The invention as set forth in claim 3 wherein said beam producing" means includes means for chopping said beam at a predetermined frequency and said amplifying means includes means tuned to said frequency to effect a rejection of spurious signals.

References Cited in the file of this patent UNITED STATES PATENTS 1,970,103 Runaldue Aug. 14 1934 2,404,147 Strickland July 16, 1946 2,879,401 Chicurela. Mar. 24, 1959 Wathen July 19, 1960 

1. AN ELECTRONIC SENSING AND SIGNALING APPARATUS COMPRISING MEANS FOR PRODUCING A BEAM OF SIGNAL RADIATION, MEANS FOR DIRECTING SAID BEAM OF RADIATION TOWARD A PATH ALONG WHICH AN OBJECT TO BE SENSED PASSES, SIGNAL PRODUCING MEANS FOR DETECTING REFLECTIONS OF SAID RADIATIONS FROM SAID PATH AND FROM SAID OBJECT TO BE SENSED, SIGNAL SELECTTING MEANS FOR DISTINGUISHING BETWEEN SIGNALS PRODUCED AS A RESULT OF REFLECTIONS FROM SAID PATH AND SIGNALS PRODUCED AS A RESULT OF REFLECTIONS FROM SAID OBJECT TO BE SENSED, MEANS RESPONSIVE TO SAID SIGNALS PRODUCED AS A RESULT OF REFLECTIONS FROM SAID PATH TO CHANGE THE INTENSITY OF THE RADIATION FROM SAID BEAM PRODUCING MEANS IN ACCORDANCE WITH CHANGES IN INTENSITY OF SAID REFLECTIONS FROM SAID PATH, AND MEANS RESPONSIVE TO SAID SIGNALS PRODUCED AS AS RESULT OF REFLECTIONS FROM SAID OBJECT TO PRODUCE AN OUTPUT SIGNAL. 